"In fact, however, as we will see in detail, there is nothing simple, nothing obvious about such attempts to explain the past.  Archaeology is currently in the midst of a great identity crisis concerning such issues as whether or not we will ever be able to explain the past in these terms and what 'explanation' is.  Physicist S.W__,* for example, has recently argued that there are no simple cause-and-effect explanations of such phenomena as ancient civilizations.  Instead, he argues, complex systems that have a determinable time-span and an evolutionary trajectory can best be understood as algorithms.  Many archaeologists have lost interest in older ideas of 'explanations' and have focused instead on how we should interpret the past." —from Robert J. Wenke and Deborah I. Olszewski, in Patterns in Prehistory: Humankind's First Three Million Years, Oxford University Press, 2007, p. 12.  *Stephen Wolfram